diff --git a/netwerk/base/LoadInfo.cpp b/netwerk/base/LoadInfo.cpp
index 4b2d68f47fb..5359994177e 100644
--- a/netwerk/base/LoadInfo.cpp
+++ b/netwerk/base/LoadInfo.cpp
@@ -340,8 +340,12 @@ LoadInfo::LoadInfo(
     if (nsMixedContentBlocker::IsUpgradableContentType(
             mInternalContentPolicyType)) {
       // Check the load is within a secure context but ignore loopback URLs
-      if (mLoadingPrincipal->GetIsOriginPotentiallyTrustworthy() &&
-          !mLoadingPrincipal->GetIsLoopbackHost()) {
+      nsCOMPtr<nsIPrincipal> precursorPrincipal =
+          mLoadingPrincipal->GetPrecursorPrincipal();
+      nsCOMPtr<nsIPrincipal> requestingPrincipal =
+          precursorPrincipal ? precursorPrincipal : mLoadingPrincipal;
+      if (requestingPrincipal->GetIsOriginPotentiallyTrustworthy() &&
+          !requestingPrincipal->GetIsLoopbackHost()) {
         if (StaticPrefs::security_mixed_content_upgrade_display_content()) {
           mBrowserUpgradeInsecureRequests = true;
         } else {